U.S. patent number 6,716,526 [Application Number 10/181,335] was granted by the patent office on 2004-04-06 for particulate compositions and their manufacture.
This patent grant is currently assigned to Ciba Specialty Chemicals Water Treatments Ltd.. Invention is credited to Howard Roger Dungworth, Rachel Clare Weston.
United States Patent |
6,716,526 |
Weston , et al. |
April 6, 2004 |
Particulate compositions and their manufacture
Abstract
A composition comprising particles which comprise a core
material within a polymeric shell, wherein the core material
comprises a hydrophobic substance, characterized in that the
polymeric shell comprises a copolymer formed from a monomer blend
which comprises, A) 30 to 90% by weight methacrylic acid B) 10 to
70% by weight alkyl ester of (meth)acrylic acid which is capable of
forming a homopolymer of glass transition temperature in excess of
60.degree. C. and C) 0 to 40% by weight other ethylenically
unsaturated monomer. The core material can comprise an active
ingredient selected from the group consisting of UV absorbers, UV
reflectors, pigments, dyes, colorants, scale inhibitors, corrosion
inhibitors, antioxidants, pour point depressants, wax deposition
inhibitors, dispersants, flame retardants, biocides, active dye
tracer materials and phase change materials. The composition has
the advantage that the polymeric shell is highly impermeable to the
core material even at elevated temperatures.
Inventors: |
Weston; Rachel Clare (Elland,
GB), Dungworth; Howard Roger (Halifax,
GB) |
Assignee: |
Ciba Specialty Chemicals Water
Treatments Ltd. (Bradford, GB)
|
Family
ID: |
9884351 |
Appl.
No.: |
10/181,335 |
Filed: |
July 17, 2002 |
PCT
Filed: |
January 16, 2001 |
PCT No.: |
PCT/EP01/00429 |
PCT
Pub. No.: |
WO01/54809 |
PCT
Pub. Date: |
August 02, 2001 |
Foreign Application Priority Data
|
|
|
|
|
Jan 27, 2000 [GB] |
|
|
0001752 |
|
Current U.S.
Class: |
428/402.2;
427/162; 427/164; 427/2.14; 427/212; 427/213.3 |
Current CPC
Class: |
C08F
291/00 (20130101); D01F 1/10 (20130101); D06M
23/12 (20130101); B01J 13/14 (20130101); C08F
291/00 (20130101); C08F 2/22 (20130101); Y10T
428/2984 (20150115); D21H 21/54 (20130101) |
Current International
Class: |
B01J
13/14 (20060101); C08F 291/00 (20060101); D06M
23/12 (20060101); D01F 1/10 (20060101); B01J
13/06 (20060101); D21H 21/00 (20060101); D21H
21/54 (20060101); B32B 027/00 (); B05D 005/02 ();
B05D 007/00 () |
Field of
Search: |
;427/2.14,162,164,212,213.3 ;428/402.2,34.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0522791 |
|
Jan 1993 |
|
EP |
|
0556367 |
|
Aug 1993 |
|
EP |
|
0959176 |
|
Nov 1999 |
|
EP |
|
Primary Examiner: Seidleck; James J.
Assistant Examiner: Tran; Thao
Attorney, Agent or Firm: Stevenson; Tyler A.
Claims
What is claimed is:
1. A composition comprising particles which comprise a core
material within a polymeric shell, wherein the core material
comprises a hydrophobic substance, characterized in that the
polymeric shell comprises a copolymer formed from a monomer blend
which comprises, A) 30 to 90% by weight methacrylic acid B) 10 to
70% by weight alkyl ester of (meth)acrylic acid which is capable of
forming a homopolymer of glass transition temperature in excess of
60.degree. C. and C) 0 to 40% by weight other ethylenically
unsaturated monomer.
2. A composition according to claim 1 in which component B is an
alkyl ester of (meth)acrylic acid which is capable of forming a
homopolymer of glass transition temperature in excess of 80.degree.
C.
3. A composition according to claim 1 in which component B of the
monomer blend is selected from the group consisting of methyl
methacrylate, acrylonitrile, tertiary butyl methacrylate, phenyl
methacrylate, cyclohexyl methacrylate and isobornyl
methacrylate.
4. A composition according to claim 1 in which component C is
selected from the group consisting of an ethylenically unsaturated
carboxylic acid and salts thereof, amino alkyl esters of
ethylenically unsaturated carboxylic acid and salts thereof,
C.sub.1-30 esters of ethylenically unsaturated carboxylic acid,
styrene, vinyl acetate and cross-linking monomer.
5. A composition according to claim 1 in which the copolymer is
formed from a monomer blend which comprises 40 to 90% of component
A and 10 to 60% of component B.
6. A composition according to claim 1 in which the copolymer is
formed from a monomer blend which comprises 45 to 90% by weight
component A and 10 to 55% of component B.
7. A composition according to claim 1 in which the polymeric shell
comprises a copolymer consisting essentially of, 45 to 90% by
weight component A and 10 to 55% by weight of component B.
8. A composition according to claim 1 in which the core consists
essentially of at least 90% by weight of the of the hydrophobic
substance.
9. A composition according to claim 1 in which the hydrophobic
substance is a non-polymeric material.
10. A composition according to claim 1 in which the hydrophobic
substance which is an oil or wax which has a melting point at a
temperature between -30.degree. C. and 150.degree. C.
11. A composition according to claim 1 in which the core material
comprises an active ingredient selected from the group consisting
of UV absorbers, UV reflectors, flame retardants, active dye tracer
materials, pigments, dyes, colorants, scale inhibitors, corrosion
inhibitors, antioxidants, pour point depressants, wax deposition
inhibitors, dispersants, biocides, enzymes, detergent builders,
fragrances, phase change materials and silicone oils.
12. A process of manufacturing a composition comprising particles,
which comprise core material within a polymeric shell, wherein the
core material comprises a hydrophobic substance, comprising the
steps, 1) forming a solution of monomer in a hydrophobic liquid, 2)
homogenizing the monomer solution into an aqueous phase to form an
emulsion, 3) subjecting the emulsion to polymerization conditions,
and 4) forming a dispersion of polymeric particles in the aqueous
phase characterized in that the polymeric shell comprises a
copolymer formed from a monomer blend which comprises, A) 30 to 90%
by weight methacrylic acid B) 10 to 70% by weight alkyl ester of
(meth)acrylic acid which is capable of forming a homopolymer of
glass transition temperature in excess of 60.degree. C. and C) 0 to
40% by weight other ethylenically unsaturated monomer.
13. A process according to claim 12 in which the copolymer is
formed from a monomer blend which comprises, 40 to 90% by weight of
component A and 10 to 60% by weight of component B.
14. A process according to claim 12 in which component B is an
alkyl ester of (meth)acrylic acid which is capable of forming a
homopolymer of glass transition temperature in excess of 80.degree.
C.
15. A process according to claim 12 in which component B is
selected from the group consisting of methyl methacrylate,
acrylonitrile, tertiary butyl methacrylate, phenyl methacrylate,
cyclohexyl methacrylate and isobornyl methacrylate.
16. A process according to claim 12 in which component C is
selected from the group consisting of an ethylenically unsaturated
carboxylic acid and salts thereof, amino alkyl esters of
ethylenically unsaturated carboxylic acid and salts thereof,
C.sub.1-30 esters of ethylenically unsaturated carboxylic acid,
styrene vinyl acetate and cross-linking monomer.
17. A process according to claim 12 in which the shell comprises a
copolymer consisting essentially of 45 to 90% by weight of
component A and 10 to 55% by weight of component B.
18. A process accordipg to claim 12 in which the core consists
essentially of at least 90% by weight of the hydrophobic
substance.
19. A process according to claim 12 in which the hydrophobic
substance is a non-polymeric material.
20. A process according to claim 12 in which the hydrophobic
substance which is an oil or wax which has a melting point at a
temperature between -30.degree. C. and 150.degree. C.
21. A process according to claim 12 in which the core material
comprises an active ingredient selected from the group consisting
of UV absorbers, UV reflectors, pigments, dyes, colorants, scale
inhibitors, corrosion inhibitors, biocides, enzymes, detergent
builders, fragrances, antioxidants, pour point depressants, wax
deposition inhibitors, dispersants, flame retardants, active dye
tracer materials, phase change materials and silicone oils.
22. An article comprising a particulate composition comprising a
polymeric shell, in which the core material comprises a hydrophobic
substance, characterized in that the polymeric shell comprises a
copolymer formed from a monomer blend which comprises, A) 30 to 90%
by weight methacrylic acid B) 10 to 70% by weight alkyl ester of
(meth)acrylic acid which is capable of forming a homopolymer of
glass transition temperature in excess of 60.degree. C. and C) 0 to
40% by weight other ethylenically unsaturated monomer.
23. An article according to claim 22 which is a textile product or
a paper or board packaging material.
24. A fiber which comprises a particulate composition comprising a
polymeric shell, in which the core material comprises a hydrophobic
substance, characterized in that the polymeric shell comprises a
copolymer formed from a monomer blend which comprises, A) 30 to 90%
by weight methacrylic acid B) 10 to 70% by weight alkyl ester of
(meth)acrylic acid which is capable of forming a homopolymer of
glass transition temperature in excess of 60.degree. C. and C) 0 to
40% by weight other ethylenically unsaturated monomer.
25. A process of forming a fiber containing particles comprising a
core material within a polymeric shell in which the core material
comprises a hydrophobic substance comprising the steps of, 1)
combining said particles with a liquid spinning dope, 2) extruding
the spinning dope, 3) passing extruded dope through an atmosphere
at a temperature of at least 150.degree. C. and 4) collecting
formed fibers,
characterized and wherein the polymeric shell that has been formed
from a copolymer derived from a monomer blend which comprises, A)
30 to 90% by weight methacrylic acid B) 10 to 70% by weight alkyl
ester of (meth)acrylic acid which is capable of forming a
homopolymer of glass transition temperature in excess of 60.degree.
C. and 0 to 40% by weight other ethylenically unsaturated monomer.
Description
This invention relates to particulate compositions comprising a
core of hydrophobic material within a shell of polymeric material
and a process of producing said compositions. The invention also
relates to novel articles comprising said compositions and in
particular novel fibres comprising said compositions and a process
for making said fibres. In the invention the core may comprise an
active ingredient such as ultra violet (UV) absorbers, flame
retardants or phase change substances. Desirably the particulate
compositions can easily be incorporated into a variety of products
such as coatings, sun-screens or a variety of textile products.
There are many instances where it would be desirable to provide
capsules comprising a shell surrounding a core material. For
instance the core may comprise an active ingredient which is
released slowly, such as fragrances, pesticides, medicaments and
the like. In other instances it may be desirable for the core
material encapsulated within the shell to remain substantially
intact either permanently or at least until a suitable trigger
induces the core to be released. There are instances where it is
important that the core material is not released from the capsules.
This includes for example encapsulated ultra violet light absorbers
for use in sunscreens and articles of clothing.
Another important application includes encapsulated phase change
materials which can be used as thermal energy storage products.
Such products include fabrics and especially clothing. Of
particular value are for example microcapsules comprising a phase
change hydrocarbon material which are combined with a fibre
spinning dope, which is then extruded to form filaments which are
cured and then collected. Since the spinning process normally
requires passing the extruded dope into an environment at
temperatures often in excess of say 150 or 200.degree. C. and can
be even as high as 350.degree. C. or higher, it is desirable for
substantially all of the core material to be retained in the shell.
Fibres such as nylon and polyester fibres are produced by melt spun
process, which generally involves very high temperatures, for
instance in excess of 300 or 350.degree. C. However, it is
difficult to find the right chemistry that provides an impervious,
durable shell wall that can be incorporated into fibres, without
suffering deleterious effects during the spinning process.
Various methods for making capsules have been proposed in the
literature. For instance it is known to encapsulate hydrophobic
liquids by dispersing the hydrophobic liquid into an aqueous medium
containing a melamine formaldehyde pre-condensate and then reducing
the pH resulting in an impervious aminoplast resin shell wall
surrounding the hydrophobic liquid. Variations of this type of
process are described in GB-A-2073132, AU-A-27028/88 and
GB-A-1507739, in which the capsules are preferably used to provide
encapsulated inks for use in pressure sensitive carbonless copy
paper.
However, although capsules based on melamine formaldehyde resins
are both impervious and durable, they tend to suffer the
disadvantage that they are less impermeable at elevated
temperatures. In addition there is also a risk that at elevated
temperatures formaldehyde is evolved.
WO-A-9924525 describes microcapsules containing as a core a
lipophilic latent heat storage material with a phase transition at
-20 to 120.degree. C. The capsules are formed by polymerizing 30 to
100 wt. % C.sub.1-24 alkyl ester of (meth)acrylic acid, up to 80
wt. % of a di- or multifunctional monomer and up to 40 wt. % of
other monomers. The microcapsules are said to be used in mineral
molded articles. However, the specific polymer compositions
described would not be suitable for exposure to high temperatures
since the lipophilic phase change material would be very quickly
lost.
There exists a need for particles that comprise a substantially
impervious shell wall that retains a hydrophobic material,
especially at elevated temperatures. There is a particular need to
provide such particles that do not release the core material even
when exposed to the harsh conditions, for instance high
temperature, high pressures and shearing conditions of producing
synthetic fibres.
There also exists a need for particles that do not release the core
material until there has been a suitable release trigger, for
instance pH. Nevertheless, the core material would not be released
in the absence of the trigger. There is also a need to achieve all
of these objectives but avoiding the use of formaldehyde
condensation products.
Thus according to the present invention we provide a composition
comprising particles which comprise a core material within a
polymeric shell, wherein the core material comprises a hydrophobic
substance, characterized in that the polymeric shell comprises a
copolymer formed from a monomer blend which comprises, A) 30 to 90%
by weight methacrylic acid B) 10 to 70% by weight alkyl ester of
(meth)acrylic acid which is capable of forming a homopolymer of
glass transition temperature in excess of 60.degree. C. and C) 0 to
40% by weight other ethylenically unsaturated monomer.
Also included in the present invention is a process of
manufacturing a composition comprising particles which comprise a
core material within a polymeric shell, wherein the core material
comprises a hydrophobic substance, comprising the steps, 1) forming
a solution of monomer in the hydrophobic liquid, 2) homogenising
the monomer solution into an aqueous phase to form an emulsion, 3)
subjecting the emulsion to polymerization conditions, and 4)
forming a dispersion of polymeric particles in the aqueous phase
characterized in that the polymeric shell comprises a copolymer
formed from a monomer blend which comprises, A) 30 to 90% by weight
methacrylic acid B) 10 to 70% by weight alkyl ester of
(meth)acrylic acid which is capable of forming a homopolymer of
glass transition temperature in excess of 60.degree. C. and C) 0 to
40% by weight other ethylenically unsaturated monomer.
The process may employ an emulsifying system, for instance
emulsifiers, other surfactants and/or polymerization stabilizers.
Thus in a preferred form of the invention an emulsifier, which may
have a high HLB is dissolved into water prior to emulsification of
the monomer solution. Alternatively the monomer solution may be
emulsified into water with a polymerization stabilizer dissolved
therein. The polymerisation stabiliser can be a hydrophilic
polymer, for example a polymer containing pendant hydroxyl groups,
for instance a polyvinyl alcohol and hydroxyethylcellulose.
Generally it is preferred to use polyvinyl alcohol which has been
derived from polyvinyl acetate, wherein between 85 and 95%,
preferably 90% of the vinyl acetate groups have been hydrolysed to
vinyl alcohol units. The polymerisation step may be effected by
subjecting the aqueous monomer solution to any conventional
polymerisation conditions. Generally polymerisation is effected by
the use of suitable initiator compounds. Desirably this may be
achieved by the use of redox initiators and/or thermal initiators.
Typically redox initiators include a reducing agent such as sodium
sulphite, sulphur dioxide and an oxidising compound such as
ammonium persulphate or a suitable peroxy compound, such as
tertiary butyl hydroperoxide etc. Redox initiation may employ up to
1000 ppm, typically in the range 1 to 100 ppm, normally in the
range 4 to 50 ppm.
Preferably the polymerisation step is effected by employing a
thermal initiator alone or in combination with other initiator
systems, for instance redox initiators. Thermal initiators would
include any suitable initiator compound that releases radicals at
an elevated temperature, for instance azo compounds, such as
azobisisobutyronitrile (AZDN), 4,4'-azobis-(4-cyanovalereic acid)
(ACVA) or t-butyl perpivilate. Typically thermal initiators are
used in an amount of up 50,000 ppm, based on weight of monomer. In
most cases, however, thermal initiators are used in the range 5,000
to 15,000 ppm, preferably around 10,000 ppm. Preferably a suitable
thermal initiator with the monomer prior to emulsification and
polymerisation is effected by heating the emulsion to a suitable
temperature, for instance 50 or 60.degree. C. or higher.
We have found that polymers formed from the special combination of
methacrylic acid and the specific category of (meth) acrylic esters
that are capable of forming a homopolymer of glass transition
temperature in excess of 60.degree. C. exhibit considerably
improved performance in regard to the impermeability to the core
material, especially at elevated temperatures. Capsules formed from
the defined proportions of methacrylic acid and said (meth) acrylic
esters have been shown to retain significantly more hydrophobic
material than other copolymers where one or both of these monomers
are replaced.
Glass transition temperature (Tg) for a polymer is defined in the
Encyclopedia of Chemical Technology, Volume 19, fourth edition,
page 891 as the temperature below which (1) the transitional motion
of entire molecules and (2) the coiling and uncoiling of 40 to 50
carbon atom segments of chains are both frozen. Thus below its Tg a
polymer would not to exhibit flow or rubber elasticity. The Tg of a
polymer may be determined using Differential Scanning Calorimetry
(DSC). Thus a reference sample with known Tg and the experimental
sample are heated separately but in parallel according to a linear
temperature programme. The two heaters maintain the two samples at
identical temperatures. The power supplied to the two heaters to
achieve this is monitored and the difference between them plotted
as a function of reference temperature which translates as a
recording of the specific heat as a function of temperature. As the
reference temperature is increased or decreased and the
experimental sample approaches a transition the amount of heat
required to maintain the temperature will be greater or lesser
depending on whether the transition is endothermic or exothermic. A
typical plot indicating the glass transition temperature is shown
in FIG. 1.
The composition of the present invention may comprise particles in
which the average particle size diameter is less than 10 microns.
Generally the average particle size diameter tends to be much
smaller, often less than 2 microns and typically the average
particle diameter will be between 200 nm and 2 microns. Preferably
the average particle size diameter is in the range 500 nm and 1.5
microns usually around 1 micron. Average particle size is
determined by a Coulter particle size analyser according to
standard procedures well documented in the literature.
Without being limited to theory it is believed that the particular
combination of methacrylic acid and said (meth)acrylic esters
provides polymers with the right degree of hydrophilicity and
hardness that seems to be responsible for the improvements in
impermeability to the hydrophobic core material.
Thus it is essential to the invention that the polymeric shell of
the particles are formed from between 30 and 90% by weight
methacrylic acid. It has been found that polymers greater than 90%
methacrylic acid or less than 30% methacrylic acid exhibit
unacceptable permeability.
In addition it is important to the invention that the polymer is
formed from between 10 and 70% by weight of the specific category
of (meth)acrylic esters, defined as monomers that are capable of
forming a homopolymer that has a glass transition temperature (Tg)
of at least 60.degree. C., preferably at least 80.degree. C.
Specific examples of said (meth)acrylic monomers include methyl
methacrylate, tertiary butyl methacrylate, phenyl methacrylate,
cyclohexyl methacrylate and isobornyl methacrylate.
It has been found that it is not possible to replace the (meth)
acrylic acid esters with ethylenically unsaturated carboxylic acid
esters that are not capable of forming a hompolymer that has a
glass transition temperature of at least 60.degree. C. without
adversely increasing the permeability of the polymer. For instance
substituting the (meth)acrylic esters of the present invention by
other (meth)acrylic esters, for instance ethyl acrylate or propyl
acrylate would not produce the desired polymer.
Therefore in a preferred form of the invention we claim a
composition wherein the copolymer is formed from a monomer blend
which comprises, A) 40 to 90%, preferably 45 to 90% by weight
(meth)acrylic acid B) 10 to 60%, preferably 10 to 55% by weight
alkyl ester of (meth)acrylic acid which is capable of forming a
homopolymer of glass transition temperature in excess of 60.degree.
C. and C) 0 to 40, preferably 0 to 20% by weight other
ethylenically unsaturated monomer.
The polymer of the present invention comprises 0 to 40% by weight
other ethylenically unsaturated monomers. Typically this monomer
may be any ethylenically unsaturated monomer that does not exert a
deleterious effect on the performance of the polymer. Typically
these other monomers include esters selected from the group
consisting of an ethylenically unsaturated carboxylic acid and
salts thereof, amino alkyl esters of ethylenically unsaturated
carboxylic acid and salts thereof, C.sub.1-30 esters of
ethylenically unsaturated carboxylic acid, styrene, acrylonitrile,
vinyl acetate and cross-linking monomers. Preferably the polymer
comprises less than 20% of other monomers. Generally the polymer of
the present invention contains less than 5 or 10% by weight other
monomers and most preferably the polymer contains substantially no
additional monomer.
It may be desirable for the polymeric shell to be cross-linked.
Generally this would be achieved by including a suitable
cross-linking monomer in the monomer mixture. Typically the
cross-linking monomer includes di- or multifunctional monomers,
which would usually bear at least two ethylenically unsaturated
groups. The cross-linking monomer may be any suitable monomer
compatible with the monomer mixture and which does not detract from
the desired properties of the polymer, especially with respect to
an undesirable increase in permeability towards to the core
material. Particularly suitable monomers include divinyl benzene,
polyethylene glycol di(meth)acrylate, triallylamine and
methylenebisacrylamide. Particularly preferred is divinyl benzene.
Suitable cross-linking monomers may be used in any amount up to 40%
by weight, for example as the sole additional monomer.
Alternatively the cross-linking monomer may be used in addition to
other additional monomers. Preferably the cross-linking monomer may
be used in any amount up to 20 or 30% by weight. Generally the
amount of cross-linking monomer is less that 5 or 10%. Most
preferably the monomer mixture does not contain any substantial
amount of cross-linking monomer.
Thus in an especially preferred form of the invention we claim a
composition wherein the copolymer is formed from a monomer blend
which consists essentially of, A) 45 to 90% by weight (meth)acrylic
acid and B) 10 to 55% by weight alkyl ester of (meth)acrylic acid
which is capable of forming a homopolymer of glass transition
temperature in excess of 60.degree. C., preferably above 80.degree.
C. Most preferably this acrylic ester is selected from the group
consisting essentially of methyl methacrylate, tertiary butyl
methacrylate, phenyl methacrylate, cyclohexyl methacrylate and
isobornyl methacrylate.
The composition of the present invention provides a particulate
composition comprising core material within a polymeric shell,
wherein the core material comprises a hydrophobic substance
polymeric material. Desirably a substantial proportion of the core
consists of the hydrophobic substance. Other materials may be
included in the core, for instance additives which modify the
properties of the hydrophobic substance. The other materials
present in the core material may be hydrophilic and suspended in
the hydrophobic substance, for instance inorganic salt hydrates.
Alternatively the other additives may be polymeric additives which
are miscible or soluble in the hydrophobic substance. Generally
where included in the core these other materials will form no more
than 10% by weight of the total core material. Often the other
materials form less than 5% of the core normally less than 2%, for
instance 0.5 to 1.5%. Thus the core will generally comprise at
least 90% of the hydrophobic substance. Preferably the amount of
hydrophobic substance comprised in the core will be more than 95%
by weight, more preferably more than 98%, in particular 98.5 to
99.5%.
The core material may comprise an active ingredient selected from
the group consisting of UV absorbers, UV reflectors, flame
retardants, active dye tracer materials, pigments, dyes, colorants,
enzymes, detergent builders and fragrances. Generally within the
context of the present invention it would be unnecessary for the
active ingredient to be released. For instance encapsulated
pigments may be used in pigmented articles, such as ceramics, where
it would be important for the pigment not to be released. There is
also an application for encapsulated colorants, i.e. dyes and
pigments for many other applications, for instance in preparing
textile products. Thus the particles comprising a pigment or dye
can be incorporated into or adhered to a fibre or textile article.
The color would be held by the particle and there would be no risk
of color leaching. Alternatively the encapsulated colorant may be
applied to packaging materials, for instance food packaging. Thus
shaded paper or board used in food packaging may be prepared by
including the encapsulated pigments or dyes into the paper making
process. Typically the colorants can be C.I. Pigment Violet 19,
C.I. Pigment Blue 15, C.I. Pigment Blue 60, C.I. Pigment Red 177 as
described in WO-A-00/61689
Alternative applications of encapsulated pigments includes
cosmetics, for instance as described in U.S. Pat. Nos. 5,382,433,
5,320,835 or WO-A-98/50002. Typically the colorants can be mica,
talc, D&C Red 7 Calcium Lake, D&C Red 6 Barium Lake, Iron
Oxide Red, Iron Oxide Yellow, D&C Red 6 Barfum Lake, Timiron
MP-1001, Mineral (Carnation White), Helindon Pink, Red 218, Japan
Blue No.1 Al lake, Polysiloxane-treated Titanium mica.
In a further aspect of the invention we provide particles which no
not release the core material and/or active ingredient until a
suitable trigger mechanism has occurred. In this case the trigger
is an increase in pH to above pH 10.
Thus such alkali releasable particles may be applied in a variety
of applications where the use of high pH may be used as a release
mechanism. In one application the active ingredient may be for
instance a lipophilic compound that is soluble in refined or crude
oil, and examples of oil containing environments into which it is
to be released include downhole and pipeline. Desirably such
lipophilic compounds are selected from wax deposition inhibitors,
pour point depressants, demulsifiers, scale inhibitors corrosion
inhibitors, biocides, enzymes, surfactants, antioxidants. The
particles will desirably release the active ingredient upon
increasing the pH to above pH 10. Thus the particles may be
injected into a subterranean reservoir under neutral of acid
conditions. The capsules may release the active ingredient upon
subsequent injection of aqueous alkali, for example as part of an
alkali flooding process.
The active ingredient may also be a substance that is to be
released in to an aqueous environment. This may be recirculating
water such as in cooling water systems, which are normally operated
under alkali conditions. Suitable actives for release into aqueous
systems include antiscalents, corrosion inhibitors, biocides,
dispersants, and antioxidants.
Generally the hydrophobic substance comprised in the core may be an
organic material. For instance the hydrophobic substance may be an
oil or a wax. Preferably the hydrophobic substance is a
non-polymeric material. The oil or wax may contain active
materials, such as UV absorbers, UV reflectors, or flame retardants
dispersed or dissolved therein. Thus the core material may a
homogenous or alternatively may comprise a dispersion of solid
active material dispersed throughout a continuous core medium of
hydrophobic substance. When the core material comprises a phase
change material, generally the phase change material is an oil or a
wax which is liquid at a temperature between -30.degree. C. and
150.degree. C.
Typical examples of flame retardants suitable for the present
invention include bromobenzoates as described in U.S. Pat. No.
5,728,760 and halogenated phosphates, thiophosphates or
thiophosphoryl chlorides as given in U.S. Pat. No. 3,912,792.
Suitable ultra violet light absorbers of the present invention
include naphthalene-methylenemalonic diesters, for instance as
mentioned in U.S. Pat. No. 5,508,025 or compositions comprising
mixtures of benzotriazoles and 2-hydroxy benzophenones as claimed
by U.S. Pat. No. 5,498,345.
When the core material is a phase change substance it may be for
instance any known hydrocarbon that melts at a temperature of
between -30 and 150.degree. C. Generally the substance is a wax or
an oil and preferably has a melting point at between 20 and
80.degree. C., often around 40.degree. C. Desirably the phase
change substance may be a C.sub.8-40 alkane or may be a
cycloalkane. Suitable phase change materials includes all isomers
of the alkanes or cycloalkanes. In addition it may also be
desirably to use mixtures of these alkanes or cycloalkanes. The
phase change material may be for instance any of the compounds
selected from n-octadecane, n-tetradecane, n-pentadecance,
n-heptadecane, n-octadecane, n-nonadecane, n-docosane, n-tricosane,
n-pentacosane, n-hexacosane, cyclohexane, cyclooctane, cyclodecane
and also isomers and/or mixtures thereof.
In a preferred form of the invention the core consists essentially
of a hydrophobic substance, for instance at least 90%, which is a
non-polymeric material, for instance an oil or wax, in particular a
phase change material. Although the preferred hydrophobic substance
is a phase change material which is essentially non-polymeric, it
is within the scope of the present invention for a smaller amounts
of polymeric additives to be included within the phase change
non-polymeric material. Usually this will be in amounts of less
than 10% by total weight of core and often will be less than 5, for
instance 0.5 to 1.5 or 2% by weight. A particularly desirable
polymeric additive is a substance that will modify the properties
of the phase change material. For instance it is known that the
temperature at which a phase change material melts on absorbing
heat can be significantly different from the temperature at which
it solidifies when losing heat. Thus a particularly desirable
polymeric additive would be a substance which will bring the
melting and solidifying temperatures closer together. This
minimization of the shift in melting/freezing point of the phase
change material may be important in various domestic applications
or for garments.
Alternatively the phase change material comprised in the core could
be a substance other than a hydrocarbon. The phase change material
could be an inorganic substance that absorbs and desorbs latent
heat during a liquefying and solidifying phase transition. The
inorganic substance may be a compound which releases or absorbs
heat during a dissolving/crystallization transition. Such inorganic
compounds include for instance sodium sulphate decahydrate or
calcium chloride hexahydrate. Thus the inorganic phase change
material may be any inorganic substance that can absorb or desorb
thermal energy during a transition at a particular temperature. The
inorganic phase change material may be in the form of finely
dispersed crystals which are dispersed throughout the core matrix
which comprises a hydrophobic substance. In one form the inorganic
phase change material is dispersed throughout a solid hydrophobic
substance such as a wax. Alternatively the hydrophobic substance
comprised in the core remains substantially liquid and contains
crystals of the inorganic phase change material dispersed
throughout the liquid. Preferably the hydrophobic liquid is a
hydrocarbon. During a phase change the crystals become liquid
droplets dispersed throughout the liquid. It may be advantageous to
include a suitable surfactant, such as a water in oil emulsifier
into the hydrophobic liquid in order to prevent coalescence of the
dispersed droplets of liquid. Preferably the inorganic phase change
material is dispersed throughout a matrix of hydrocarbon phase
change material which is a wax or an oil. In this preferred
embodiment the hydrocarbon and inorganic materials may both absorb
or desorb heat. Alternatively the hydrocarbon phase may be a
carrier oil that is not necessarily a phase change material. In
this instance the carrier oil may be a process aid.
According to the present invention we have found that it is
possible to produce a particulate composition comprising a core
material held within a polymeric shell, which at least 98% of the
core material is retained when exposing the particulate composition
to a temperature of 200.degree. C. for 15 minutes. In general the
particulate material will retain at least 98%, 99% or even 100% of
the core material on exposure to a temperature of 200.degree. C.
for 15 minutes. Thus we provide a particulate composition in which
none or virtually none of the core material is lost when exposed to
elevated temperatures.
It is possible to incorporate the particles of the present
invention into any suitable article, for instance fibres, textile
products, ceramics, coatings etc. Thus a further aspect of the
present invention we provide an article comprising particles with a
core of core material and a polymeric shell. Hence according to the
invention it is possible to provide an article which comprises
encapsulated flame retardants, UV absorbers, active dye tracer
materials or phase change material. In the case of encapsulated
flame retardants it would be desirable for the flame retardant to
be retained during any processing steps such as fibre formation,
involving temperatures of say between 150.degree. C. to about
350.degree. C. but then released when exposed to the excessive
temperatures in excess of say above 400 or 500.degree. C. In a
preferred embodiment of the invention the polymer particles
comprise a core material that contains both a phase change
material, which is a wax or an oil and dispersed or dissolved
therein a flame retarding substance. Thus in one preferred form of
the invention the presence of the flame retardant in the capsule
would prevent or reduce the risk of phase change material from
igniting if released under excessive temperatures.
Particularly important articles according to this aspect of the
invention are fibres and fabrics formed from said fibres, wherein
the fibres comprise particles of the present invention composition
each comprising core material within a polymeric shell, wherein the
core material comprises a hydrophobic substance. In this aspect of
the invention the fibres comprise said particles distributed within
the matrix of the fibre. Generally the diameters of the particles
should be less than half of the cross-sectional diameter of the
fibre. Generally if the particles are much larger there is a risk
that the presence of such large particles in the fibres could
result in the fibres which tend to break at the position of the
particle. Typically the particles will have a particle size
diameter less than 30%, preferably less than 10% of the diameter of
the fibre.
The fibres comprising the particles of the present invention are
made my incorporating the particles into the spinning dope. The
spinning dope can then be spun according to standard spinning
techniques, for instance as described in EP-A-269393. Generally the
spinning dope is then passed through an orifice into a heated
atmosphere where the extruded dope is cured to form a fibre, which
is then collected.
The particles comprised in the composition of the present invention
are suitable for incorporating into any fibres, for instance
acrylics, polyesters, nylon, polypropylene.
According to this aspect of the invention we provide a process of
forming a fibre containing particles comprising a core material
within a polymeric shell wherein the core material comprises a
hydrophobic substance comprising the steps of, 1) combining said
particles with a liquid spinning dope, 2) extruding the spinning
dope, 3) passing extruded dope through an atmosphere at a
temperature of at least 150.degree. C. and 4) collecting formed
fibres,
characterized and wherein the polymeric shell that has been formed
from a copolymer derived from a monomer blend which comprises, A)
30 to 90% by weight methacrylic acid B) 10 to 70% by weight alkyl
ester of (meth)acrylic acid which is capable of forming a
homopolymer of glass transition temperature in excess of 60.degree.
C. and 0 to 40% by weight other ethylenically unsaturated
monomer.
Desirably the polymeric particles are sufficiently impermeable to
the hydrophobic substance contained in the core so that during the
formation of the fibre the high temperature conditions do not
result in any significant loss of the hydrophobic substance. We
have surprisingly found that the core material is able to retain
most or all of the core material even when the polymeric particles
are exposed to a spinning temperature in excess of 150.degree. C.
This has also been found to be the case even when the spinning
temperature is much higher, for instance in excess of 200.degree.
C. Thus we find that the particles retain at least 98% by weight,
preferably 99%, of the hydrophobic substance when passed though the
spinning process.
A particularly important application of the present invention
relates to incorporation of particles in fibres, which particles
contain a phase change substance as the core material. The
durability and impermeability of the polymeric shell towards the
phase change material enables the particles to be incorporated into
fibres without any significant loss of the phase change material.
The impregnated fibres containing phase change material can then be
woven into textile products. The textile products can include items
of clothing and other fabrics.
The present invention also contemplates applying a dispersion of
the encapsulated material onto the fibres or preferably onto the
textile products. This would normally be followed by drying to
remove the carrier liquid. Typically the carrier liquid may be an
aqueous liquid, optionally containing volatile water miscible
organic liquid, to assist the drying process. The coating
formulation comprising said capsules may additionally contain other
additives, for instance binders. The drying process would normally
involve subjecting the fibre or textile product to an atmosphere
which has an elevated temperature, often above 80.degree. C., and
may be for instance as high as 140 to 170.degree. C. or higher.
Such coating processes are well known and described in the prior
art.
The following examples illustrate the invention.
EXAMPLE 1
An oil phase is prepared by mixing together blend of methacrylic
acid and methyl methacrylate (40:60 wt/wt) (60 g) with octadecane
(140 g) and tertiary butyl perpivilate (thermal initiator). The oil
phase is homogenized into water (660 g) containing polyvinyl
alcohol (Gohsenol GH20) (20 g) using a Silverson mixer for 5
minutes until a stable emulsion is formed. The emulsion is then
transferred into a reactor with stirrer, thermometer and nitrogen
supply and deoxygenated with nitrogen for 30 minutes. The contents
of the reactor are then heated to 60.degree. C. and maintained at
this temperature for 2 hours after which the contents are heated to
80.degree. C. and then maintained for a further 1 hour before being
cooled and filtered. The resulting emulsion contains polymeric
particles each comprising a polymeric shell encapsulating the
octadecane wax having a solids content of 25.0% and a particle size
of 1.2 microns.
The particles of encapsulated wax are then subjected to
temperatures of 150.degree. C. for 15 and 30 minutes and
200.degree. C. for 15 and 30 minutes. The percentage weight loss
was measured by thermo-gravimetric analysis (TGA) and the results
are shown in Table 1.
EXAMPLES 2 to 7
Example 1 is repeated using different ratios of methyl methacrylate
and methacrylic acid. In each case the results showing the weight
loss are presented in Table 1.
TABLE 1 % weight % weight % weight % weight Copolymer loss @ loss @
loss @ loss @ Composition % 150.degree. C. for 150.degree. C. for
200.degree. C. for 200.degree. C. for Example MMA:MAA Wax 15
minutes 30 minutes 15 minutes 30 minutes 1 40:60 80 0 0 0.9 1.7 2
50:50 70 0 0 1.2 2.6 3 60:40 80 0 0.1 0.5 0.8 4 70:30 70 0 0.1 2.0
2.5 5 80:20 80 0.1 0.1 3.0 6.2 6 90:10 70 0.2 0.4 8.5 16.8 7 100:0
80 0.9 1.8 16.5 22.3 MMA - methyl methacrylate MAA - methacrylic
acid
From the results it can clearly be seen that the results in Table 1
Examples 1 to 4 give the best results, especially at 200.degree.
C.
* * * * *